THE COMPOSITION OF FEEDING STUFFS 



15 



pentosans are widely distributed in plants, and make up a consider- 

 able proportion of the nitrogen-free extract of many plants. Hay 

 from grasses contains about 20 per cent of pentosans; gluten feed, 

 17 per cent; dried brewers' grains and wheat bran, 24 per cent; 

 clover, 10 per cent; cereal straw, 22 per cent; oil meal and dried 

 distillers' grains, 13 per cent. 



The best known substances of this group are araban, found in 

 beet pulp, cherrygum, etc., and xylan or wood gum, found in wood 

 and straw. 



The pectin bodies occur especially in unripe fruits ; these sub- 

 stances are responsible for the jellying of fruit juices, which de- 

 pends upon pectin taking up water during the boiling of the fruit, 



15 20 25 30 35 40 45 50 



COTTON-SEED HULLS 



BUCKWHEAT HULLS 



OAT STRAW 



OAT HULLS 



CORN COBS 



TIMOTHY HAY 



CLOVER HAY 



CORN STALKS 



DRIED BREWERS' GRAINS 



OATS 



WHEAT BRAN 



GLUTEN FECD 



WHEAT MIDDLINGS 



BARLEY 



INDIAN CORN 



FIG. 4. Fiber in plant materials, in per cent. 



gelatinous substances being formed known as pectoses or pectic 

 acids. The mucilaginous substances of flaxseed and seeds or roots 

 of some other plants belong to this group ; these substances do not, 

 however, possess the importance that is attached to the preceding 

 three groups of compounds, starch, sugar and pentosans. 



Fiber (called crude fiber or woody fiber by some authors) 

 makes up the cell walls of the plants and is largely composed of 

 cellulose. So-called incrusting substances (lignin and cutin) are 

 always present, especially in tough, woody plant materials, like 

 husk, hulls, seed-coats, overripe hay and straw, which contain con- 

 siderable proportions of these substances in the fiber. Fiber is more 

 resistant to the action of solvents and digestive fluids than other 

 groups of plant materials. It is attacked by bacteria and possibly 



